Short-Term Effects of Nostril-Regulated Yoga Breathing on Autonomic Variables: A Randomized Crossover Trial.

Previously, autonomic changes were reported during nostrilregulated yoga breathing, although the results varied between studies. Here, to reduce variation, the nostril dominance at rest was considered while comparing the effects of nostril breathing on autonomic variables because differences in lateralized airflow were traditionally reported based on nostril dominance at rest. Forty-five participants (mean age 24.3 ± 3.8; male-to-female ratio 23:22) were assessed in sessions on five separate days in random order. The sessions (with 15 minutes of intervention) were: (1) right-uninostril breathing, or surya anuloma viloma; (2) left-uninostril breathing, or chandra anuloma viloma; (3) alternate-nostril breathing, or anuloma viloma; (4) breath awareness; and (5) quiet seated rest. Nostril patency was recorded before each session using the Zwaardemaker method. Out of 225 sessions, participants were right-nostril dominant at rest in 136 sessions and left-nostril dominant at rest in 89 sessions. Assessments included heart rate variability, blood pressure, respiration, galvanic skin conductance, finger plethysmogram amplitude, and state anxiety. Generalized linear mixed-model analyses, with fixed effects of states, sessions, and baseline nostril dominance, were performed. A significant effect of states or sessions was observed as follows. In right-nostril dominance at rest RMSSD and high-frequency heart rate variability increased during left-uninostril breathing, while systolic blood pressure decreased during left-uninostril breathing and alternate-nostril breathing (padj < 0.05 in all cases). In left-nostril dominance at rest finger plethysmogram amplitude decreased during breath awareness. The other changes were common to right-nostril dominance at rest and left-nostril dominance at rest. State-Trait Anxiety Inventory scores decreased after right-uninostril breathing, left-uninostril breathing, alternate-nostril breathing, and quiet rest in right-nostril dominance at rest and left-nostril dominance at rest (padj < 0.05 in all cases). Unique effects of uninostril or alternate-nostril breathing were clear only when preintervention nostril dominance was considered, which aligns with traditional text descriptions of physiological differences based on nostril dominance at rest. With right-nostril dominance at rest, practicing left-uninostril breathing and alternate-nostril breathing reflected relaxation, whereas the changes with left-nostril dominance at rest were less clear.